Method of and apparatus for producing reprint

ABSTRACT

In a method of producing reprints, detection is made as to data relative to an image on an original-image film, data relative to an image printed on a printed sheet of photographic paper from the original-image film and correction data representative of desired corrections to be applied to the color characteristics of the image printed on the printed sheet. On the basis of the above-mentioned data, arithmetic operations are performed upon the amount of exposure required for printing the image on the photographic paper from the original-image film. On the basis of the results of the arithmetic operations, exposure control relative to the printing is performed to finish the color characteristics of the image to be reprinted on the photographic paper so that the color characteristics includes the desired corrections applied to the color characteristics.

This is a division of application Ser. No. 07/002,365 filed Jan. 12,1987, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of and an apparatus forproducing a reprint by exposing photographic paper on the basis of imagedata relative to a printed sheet of photographic paper and correctiondata.

2. Description of the Related Art

In a typical photograph printing apparatus, light emitted from a lightsource and transmitted through an original-image film is projected ontophotographic paper by a lens unit and thus the photographic paper isexposed to an image on the film. Printing apparatus of the type that isapplied to the printing of color photographs are arranged such thatlight rays emitted from a light source illuminate an original-image filmvia a light control filter device constituted by color compensatingfilters for yellow (Y), magenta (M) and cyan (C).

In such a printing apparatus, image-density sensors constituted byphotosensitive elements such as photodiodes are interposed between theoriginal-image film and the lens unit for detecting image density datarelative to the film.

The image density data is supplied to an exposure controller, in whicharithmetic operations upon the amount of exposure relative to each colorare performed by the following equation so as to enable each photographto be printed at an optimum exposure value corresponding to the densityof each image formed on the original-image film. This is based on aknown Evans' theorem.

    log E.sub.i =log E.sub.Ni +C.sub.j (D.sub.Nj -D.sub.NNj)   (1)

where

E: amount of exposure relative to the original-image film;

E_(N) : amount of exposure relative to a normal original-image film;

C: correction factor relative to the density of the original-image film;

D_(N) : LATD of the original-image film;

D_(NN) : LATD of the normal original-image film;

i: one of red, green and blue; and

j: one of Y, M and C.

However, in actual printing, the amount of exposure calculated from theabove equation (1) may be further corrected on the basis of a correctionvalue relative to a specific image pattern. This correction is commonlyperformed by a skilled operator in order to prevent color and densityfrom being imperfectly reproduced owing to a color failure or densityfailure.

If the color characteristics, such as density, tone, hue and saturation,of an initial print produced by such a printing apparatus are imperfect,corrections are commonly made in the color characteristics and a reprintis produced. However, when such reprinting is performed on the basis ofthe LATD of the original-image film, the following problem isencountered. Even if the same printing and developing apparatus as thatused for the previous printing are employed for the present reprinting,variations occur in the operating states of the light source or exposurecontrol system of the apparatus. Therefore, if a correction value aloneis input, the finish of the reprint is likely to differ from a desiredfinish. This constitutes one cause of complaints from consumers. In aparticular case where a photograph is printed from a film having animage with an imperfect color balance, the operator makes more or lesssubjective corrections on the basis of visual checking as describedpreviously. Therefore, the same corrections as those of the initialprint are not necessarily performed in reprinting, and this constitutesanother cause of complaints from consumers.

A printer for producing reprints is commonly disposed separately from aprinter for producing initial prints at the time of film development. Itis therefore necessary to always maintain these prints under the samefinishing conditions. However, this maintenance is significantlytime-consuming.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a methodof and an apparatus for producing a reprint of a finish in which desiredcorrections are made with respect to the color characteristics of animage previously printed on a sheet of photographic paper on the basisof a set of image data relative to an original-image film and anotherset of image data relative to the printed sheet as well as another setof desired correction data relative to the corrections of the colorcharacteristics of the image printed on that sheet.

To this end, one aspect of the present invention resides in a method ofproducing a reprint comprising the steps of performing arithmeticoperations upon the amount of exposure on the basis of a set of imagedata relating to an original-image film detected by a photographprinting apparatus, another set of image data relative to a printedsheet of photographic paper which carries an image printed from theoriginal-image film, and another set of desired correction data relativeto the corrections of the color characteristics of the image carried onthe printed sheet; and performing exposure control on the basis of theresults of the arithmetic operations so that desired corrections aremade with respect to the finish of the printed sheet of photographicpaper to thereby obtain a reprint of a finish having desired colorcharacteristics.

In accordance with the above aspect of the present invention, arithmeticoperations are performed upon the amount of exposure on the basis of theset of image data (a first set of data) relative to the original-imagefilm and the set of image data (a second set of data) relative to theprinted sheet of photographic paper as well as the set of desiredcorrection data (a third set of data) relative to the colorcharacteristics of this printed sheet. Accordingly, it is possible toachieve reprints of a finish in which desired corrections are made withrespect to the finish of the printed sheet of photographic paper.

In particular, reprinting is an operation which requires significantlylaborious work as compared with initial printing in the processconducted in a processing laboratory. In an instance where a reprint ofa finish having desired color characteristics is not obtained owing tothe previously-described factors, reprinting must again be repeated andthis requires further complicated operations. In accordance with theabove aspect of the invention, reprints of a desired finish can beachieved by correcting color characteristics such as density, tone, hueand saturation. This eliminates the need for unnecessary repetition ofreprinting as well as the necessity to always maintain finishingconditions in a printer for reprinting and that for initial printingunder the same conditions.

Another aspect of the present invention resides in an apparatuscomprising film-image data detecting means for detecting image datarelative to an original-image film; paper-image data detecting means fordetecting image data relative to a printed sheet of photographic paperwhich carries an image printed from the original-image film; meansarranged to input therethrough correction data relative to the colorcharacteristics of the image carried on the printed sheet ofphotographic paper; arithmetic means for performing arithmeticoperations upon the amount of exposure required for printing on thebasis of the image data relative to the original-image film, the imagedata relative to the printed sheet of photographic paper, and thedesired correction data relative to desired corrections of the colorcharacteristics of this printed sheet; and control means for performingprinting while controlling exposure on the basis of the results of thearithmetic operations of the arithmetic means to obtain a reprint of afinish having color characteristics in which desired corrections aremade with respect to the finish of the printed sheet.

In accordance with the above aspect of the present invention, the amountof exposure is determined employing three kinds of data, a set ofdetected image data (a second set of data) relative to the printed sheetof photographic paper, another set of correction data (a third set ofdata) relative to the color characteristics of this printed sheet, andanother set of image data (a first set of data) relative to theoriginal-image film, the first set of data conventionally applied to thecorrection of the amount of exposure. Accordingly, it is possible toachieve reprints of a finish in which desired corrections are made withrespect to the finish of the printed sheet.

It is common practice to obtain the above-mentioned kinds of data, forexample, from the density of each image, i.e., the integrated density ofthe whole of each image. However, an important portion suitable fordetection of the density may be selectively measured. Therefore,detecting devices may be constituted by area sensors such as CCDs whichare previously incorporated for film photometry in some of conventionalprinting apparatus. The density of an image printed on the photographicpaper may be detected by measuring light emitted from the light sourceand reflected from the photographic paper. The correction data inputmeans may primarily be constituted by a keyboard or a rotary switch. Theprinted sheet of photographic paper for use in measuring the density ofsuch reflected light need not necessarily be one which corresponds to aframe of the original-image film to be printed. For example, it ispossible to select one from different frames having substantiallysimilar image patterns.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 diagrammatically illustrates the construction of a photographprinting apparatus constituting a preferred embodiment of the presentinvention;

FIG. 2 is a block diagram of the control circuit of the preferredembodiment;

FIG. 3 is a perspective view of a carrier for use with the preferredembodiment;

FIG. 4 is a cross section taken along the line IV--IV of FIG. 3;

FIG. 5 is a flow chart illustrating the control operations of thepreferred embodiment; and

FIG. 6 is a flow chart illustrating an exposure control subroutineincorporated in the main routine shown in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be described withreference to the accompanying drawings.

FIG. 1 diagrammatically illustrates one example of a photograph printingapparatus indicated generally at 10. As illustrated, light emitted froma light source 12 passes through a light diffusion cylinder 14 andilluminates a negative film 18 as an original-image film carried by acarrier 16. The original image is printed from the negative film 18through a lens unit 20 onto photographic paper 22.

A light control filter device 24 constituted by a combination of yellow(Y), magenta (M) and cyan (C) color compensating filters F1, F2 and F3is interposed between the light source 12 and the light diffusioncylinder 14. The color compensating filters F1, F2 and F3 of the lightcontrol filter device 24 are respectively controlled by drivers 28, 30and 32 responsive to signals supplied from an exposure controller 26.The Y, M and C filters F1, F2 and F3 serve to subtract a color componentor components which are not regarded as being required during exposureto white light.

A pair of density sensors 34 for detecting image density data relativeto three primary colors of red (R), green (G) and blue (B) are disposedbetween the negative film 18 and the lens unit 20. The density sensors34 are each constituted by an assembly of photosensitive elements suchas photodiodes. The density sensors 34 are adapted to receive lightemitted from the light source 12 and transmitted through the negativefilm 18 and supply a density distribution data signal relative to thenegative film 18 to the exposure controller 26 through an amplifier 36.

The exposure controller 26 determines a correction factor on the basisof a known Evans' theorem so as to adjust the balance of the three colorcomponents Y, M and C so that the color obtained from these componentsturns gray, and thus controls the amount of exposure E_(i) in accordancewith the previous equation (1).

After the energization of a solenoid 40 constituting one part of ashutter 38 (after the start of exposure), each time one of the colorcomponents reaches a required amount of exposure, a corresponding one ofthe color compensating filters F1, F2 and F3 of the light control filterdevice 24 is inserted into the optical path to terminate the exposure ofthe color component. Thus the total exposure period is controlled.

A photographic-paper holding portion 44 for holding a printed sheet ofphotographic paper 42 is formed in the carrier 16 which carries thenegative film 18. A sheet of the photographic paper 42 which carries animage printed from the negative film 18 is disposed in thephotographic-paper holding portion 44.

An aperture 46 is formed on the side of the carrier 16 on which theprinted surface of the photographic paper 42 loaded into thephotographic-paper holding portion 44 is exposed. The aperture 46opposes the light source 12 via an optical system such as a mirror 48and thus light rays which illuminate the negative film 18 and thosewhich illuminate the photographic paper 42 are caused to vary insubstantially the same manner as each other.

It is to be noted that the kind of optical system interposed between thelight source 12 and the photographic paper 42 is not limited solely tothe mirror 48. Other kinds of optical system such as lens units may beemployed depending upon the position at which the light source 12 isdisposed. In addition, such an optical system need not necessarily beused in a case where light emitted from the light source 12 is capableof directly illuminating both the negative film 18 and the photographicpaper 42.

A pair of density sensors 50 having the same structures as those of thedensity sensors 34 are interposed between the mirror 48 and thephotographic-paper holding portion 44 in the carrier 16. The densitysensors 50 detect the density of the printed surface of the photographicpaper 42 when the printed surface reflects illuminating light emittedfrom the light source 12 (in the present embodiment the light of a lightsource 12A, shown by an imaginary line in FIG. 1, which is reflected bythe mirror 48). It is preferable that this density be the average valueof the density of the entire image.

The density data signal detected by the density sensors 50 is suppliedthrough an amplifier 52 to the exposure controller 26. Thephotographic-paper holding portion 44 has a gray bottom surface 54.Accordingly, in a case where the photographic paper 42 is not disposedin the photographic-paper holding portion 44 during printing from thenegative film 18, a density data signal corresponding to the state whichrequires no color correction in accordance with Evans' theorem issupplied to the exposure controller 26.

As shown in FIG. 2, the exposure controller 26 includes a CPU (centralprocessing unit) 56, a RAM (random access memory) 58, a ROM (read-onlymemory) 60 and a bus 62 for connecting them, such as a data bus and acontrol bus.

A key board 90 is used to input desired correction data relative to theamount of exposure, and the output of the keyboard 90 is supplied to theexposure controller 26. The keyboard 90 normally includes a plurality ofdensity keys allocated for inputting density correction values as wellas R, G and B keys allocated for inputting correction values relative tothe respective color characteristics of the three color components. Inan instance where no correction is performed, a normal key is selectedfrom among these keys. In this instance, the color characteristics of anew print produced by reprinting are completely the same as those of theinitial print which is produced at the time of film development.

The output signals of the amplifiers 36 and 52 are respectively suppliedto an input/output port 66 via an A/D (analog/digital) converter 64. Onthe basis of these signals, further signals are supplied from theinput/output port 66 to the solenoid 40 and the drivers 28, 30 and 32.

The ROM 60 stores therein the following equation based on thepreviously-described equation (1).

    log E.sub.i =log E.sub.Ni +C.sub.j (D.sub.Ni -DNNj)+γ.sub. (D.sub.pj -D.sub.NPj)+KD·ID+K.sub.i ·I.sub.i      (2)

where

γ: color correction factor relative to the density of the photographicpaper;

D_(P) : density of the photographic paper;

D_(NP) : density of a normal photographic paper;

KD: number of steps of selected density keys (. . . -2, -1, 0, +1, +2, .. . );

K_(i) the number of steps of selected color keys (. . . -2, -1, 0, +1,+2, . . . );

ID: correction value per step of the density key; and

I_(i) : correction value per step of the color key.

On the basis of the equation (2), the CPU 56 performs arithmeticoperations upon the amount of exposure E_(i) relative to each color (i:red, green or blue) and furthermore the exposure period of each color,as well as the operating period of each of the color compensatingfilters F1, F2 and F3 of the light control filter device 24.

The carrier 16 will now be described in detail with reference to FIG. 3.

As illustrated, the carrier 16 is constituted by a base 70 and a cover72, and one longitudinal edge of the base 70 is joined to that of thecover 72 by means of hinges 74 so that their respective primary surfacesmay be moved into and out of contact with each other. A limit switch 75is mounted on the base 70 for detecting the opening and closing of thecover 72. A signal line of the limit switch 75 is connected to theexposure controller 26.

Two ridges 76 and 78 which extend parallel to the longitudinal edge ofthe base 70 are integrally formed on a portion of the base 70 which isnear this side as viewed in FIG. 3. The space between the ridges 76 and78 serves as a guide passage 80 for guiding the breadthwise edges of thenegative film 18. This construction enables the negative film 18 to bepositively moved straight in the longitudinal direction (in thedirection of an arrow A in FIG. 3).

The lengthwise mid portion of the guide passage 80 has a through-hole 82having a rectangular form corresponding to one frame of the negativefilm 18. The negative film 18 is illuminated through the through-hole 82by light emitted from the light source 12.

A through-hole 86 is formed in the cover 72 at a position thereofcorresponding to the through-hole 82, and the light rays transmittedthrough the negative film 18 are conducted through the through-hole 86toward the lens unit 20.

A frame member 88 having a substantially C-like form is attached to thecover 72 at a position thereof below the through-hole 86 as viewed inFIG. 3. As shown in FIG. 4, the frame member 88 has a substantiallyL-like cross-section which enables the photographic paper 42 to be heldin an inserted manner. The aforesaid aperture 46 is formed in the base70 at a position thereof corresponding to the portion surrounded by theframe member 88. As shown in FIG. 1, when the cover 72 is closed, theprinted surface of the photographic paper 42 is adapted to oppose themirror 48.

Specifically, when a predetermined frame of the negative film 18 islocated at the position corresponding to the through-holes 82 and 86 anda sheet of the photographic paper 42 which is previously printed fromthat frame and yet which requires correction is inserted into the framemember 88, it is possible to acquire density data relative to thisphotographic paper 42 during printing from the negative film 18.

The procedures for effecting printing in a photograph printing apparatushaving the above-described arrangement will be described with referenceto the flow chart of FIG. 5. It is assumed that the light source 12 ispreviously energized to emit light rays.

First, the negative film 18 is loaded into the carrier 16 and is movedin either the direction of the arrow A of FIG. 3 or the directionopposite thereto to cause a desired frame to correspond to thethrough-hole 82. During this movement, the breadthwise edges of thenegative film 18 are guided by the ridges 76 and 78 of the carrier 16 toenable the negative film 18 to move linearly without any zigzag motion.

After an operator has located the negative film 18 at a predeterminedposition, the operator inserts a printed sheet of the photographic paper42 corresponding to the frame of the negative film 18 into the framemember 88 and thus locates the printed sheet in the photographic-paperholding portion 44. In this manner, the carrier 16 is capable ofcarrying one pair consisting of a predetermined frame of the negativefilm 18 and the sheet of the photographic paper 42 which has beenpreviously printed from that frame but which requires correction becauseof the imperfect quality of its printing. This facilitates operationssuch as checking.

After completion of the above-described preparation step, in Step 104,the cover member 72 of the carrier 16 is rotated about the pivot axis ofthe hinges 74 and is thus superimposed on the base 70. When the limitswitch 75 detects this closed state, the process proceeds to Step 105.In Step 105, correction values relative to the color characteristics ofthe printed sheet of the photographic paper 42, such as density, tone,hue and saturation, are input through the keyboard 90. Thus desiredcorrection data is stored in the exposure controller 26. In Step 106,the density sensors 34 detect the density of the frame of the negativefilm 18 on the basis of the light which is transmitted through thenegative film 18 after emitted from the light source 12. Simultaneously,light rays emitted from the light source 12 are reflected from themirror 48 to illuminate the photographic paper 42. The light rays arereflected from the photographic paper 42 and thus the density of theimage printed on the photographic paper 42 is detected by the densitysensors 50.

In an instance where the densities of the negative film and thephotographic paper are detected employing separate light sources, thedetection result may be influenced by variations in the intensity ofeach lamp used as the light sources. In this embodiment, however, thedensities of the negative film 18 and the photographic paper 42 aredetected employing the same light source. It is therefore possible toeliminate such an influence and to reduce the level of electrical powerrequired for energization of the light source.

In this embodiment, the densities of the negative film 18 and thephotographic paper 42 which are detected by the density sensors 34 and50 are illustratively obtained from the average values of the densitiesrelative to the entire images of them. However, each of the densitiesmay be obtained by measuring one important portion of each of thenegative film 18 and the photographic paper 42. Also, in an instancewhere the photographic-paper 42 is not disposed in thephotographic-paper holding portion 44, the density detected by thedensity sensors 50 is substantially equal to that of the normalphotographic paper since the bottom surface 54 of the photographic-paperholding portion 44 is gray.

In Step 108, the amount of exposure relative to each color is calculatedusing the equation (2) on the basis of the respective densities detectedin Step 106 and the data relative to the correction values input in Step105. Also, in a case where the photographic paper 42 is not disposed asdescribed previously, the respective amounts of exposure are calculatedusing the previously-mentioned equation (1).

Each of the exposure amounts calculated in Step 108 is converted into acorresponding exposure period. In Step 110, the exposure periods aresorted in ascending order. Then, in Step 112, the shutter 38 is opened(the solenoid 40 is energized). Thus the light transmitted through thepredetermined frame of the negative film 18 is projected through thelens unit 20 onto the photographic paper 22 and the exposure thereof isstarted.

In Step 114, each of the light compensating filters F1, F2 and F3 of thelight control filter device 24 is operated for a predetermined period sothat, each time the exposure of one color is completed, the color is cutoff. When the exposure of all colors is completed, the process proceedsto Step 116, in which the shutter 38 is closed. This operation will bedescribed later.

In Step 118, when the limit switch 75 detects the fact that the operatoropens the carrier 16, printing is completed. Subsequently, when anotheroriginal-image film or another frame of the negative film 18 and anothersheet of the photographic paper 42 are loaded into the carrier 16 andthe carrier 16 is closed, printing is restarted.

The subroutine of the Step 114 will now be described in detail withreference to FIG. 6.

In Step 110 the color compensating filters of the light control filterdevice 24 are rearranged in an ascending order of an exposure period,for example, in the following order, the yellow filter F1, the magentafilter F2 and the cyan filter F3. Judgement is made in Step 122 as towhether or not the period allocated for the exposure of yellow haspassed. If it is judged that the period has passed, a signal is fed fromthe exposure controller 26 to the driver 28 in Step 124 and the filterF1 is inserted into the optical path. Then, if it is judged in Step 126that the period allocated for the exposure of magenta has passed, thedriver 30 is operated in Step 128 and the filter F2 is inserted into theoptical path. Similarly, if it is judged in Step 130 that the cyanexposure period which is the longest exposure period of the three haspassed, the driver 32 is operated in Step 123 to insert the filter F3into the optical path. Subsequently, the process returns to the mainroutine.

In this manner, the color compensating filters of the light controlfilter device 24 are controlled in accordance with the density of theprinted sheet of the photographic paper 42 as well as the density of thenegative film 18. Accordingly, a reprint can be produced in whichdesired corrections are made in the color characteristics of the printedsheet of the photographic paper 42 (for example, a sheet of photographicpaper which carries an image printed at the time of film development).

Since the light source 12 is used as a common light source for thenegative film 18 and the photographic paper 42, there is no variation inchromaticity and, in addition, cost can be reduced as compared with thecase where a separate light source is disposed for each of them.

The negative film 18 and a corresponding printed sheet of thephotographic paper 42 can be easily compared with each other duringreprinting since the carrier 16 is capable of carrying a pair of thenegative film 18 and the photographic paper 42.

The presently preferred embodiment is arranged to sequentially detectthe density of the photographic paper 42 by way of example. However,density data relative to the photographic paper 42 may be measured by aseparate measuring device and the density data is recorded on arecording medium such as magnetic tape, and required density data may beinput to the exposure controller 26 on the basis of the recording. Also,although the light source 12 is used in common to illuminate thenegative film 18 and the photographic paper 42, light sources may ofcourse be separately provided for the original-image film 18 and thephotographic paper 42.

As described above, the method of and the apparatus for producing areprint in accordance with the present invention provides the excellenteffect of always producing a reprint of a finish in which desiredcorrections are made on the basis of image data relative to theoriginal-image film and image data relative to the printed sheet ofphotographic paper as well as desired correction data relative to thecolor characteristics of the image on the printed sheet of thephotographic paper.

In addition, printers having the present inventive functions are of afull correction type in which reprints of a finish having desired colorcharacteristics can be produced from any type of negative images. It istherefore possible to completely eliminate the influences of adifference between kinds of negative film, variations in the colorcharacteristics of a negative film with time and so forth. Accordingly,since finishing conditions can be set through a single channel, simpleand easy maintenance of a printer is enabled.

What is claimed is:
 1. A method of producing a reprint, comprising thesteps of:(a) performing arithmetic operations upon the amount ofexposure required for printing an image on photographic paper from anoriginal-image film on the basis of a set of data (a first set of data)relative to said image on said original-image film, another set of data(a second set of data) relative to an image printed on a printed sheetof photographic paper from said original-image film, and another set ofcorrection data (a third set of data) representative of desiredcorrections to be made with respect to the color characteristics of saidimage printed on said printed sheet; and (b) performing exposure controlon the basis of the results of said arithmetic operations to finish thecolor characteristics of said image to be reprinted on said photographicpaper so that said color characteristics includes said desiredcorrections applied to said color characteristics of said image printedon said printed sheet.
 2. A method of producing a reprint according toclaim 1, wherein said step (a) includes the steps of (c) detecting saidfirst set of data, (d) detecting said second set of data, and (e)inputting said third set of data.
 3. A method of producing a reprintaccording to claim 2, wherein in a case wherein said steps (c) and (d)are performed, both said image on said original-image film and saidimage on said printed sheet are illuminated under the same conditions.4. A method of producing a reprint according to claim 3, wherein saidfirst set of data includes density data relative to said image formed onsaid original-image film and said second set of data includes densitydata relative to said image formed on said printed sheet.
 5. A method ofproducing a reprint according to claim 4, wherein said exposure controlis performed by moving each filter of a light control filter device intoand out of an optical path extending between said image on saidoriginal-image film and a light source for illuminating said image andat the same time opening and closing said optical path by means of ashutter.
 6. A method of producing a reprint according to claim 5,wherein said step (c) is performed by detecting light emitted from saidlight source and transmitted through said original-image film and saidstep (d) is performed by detecting light emitted from said light sourceand reflected from said printed sheet of photographic paper.
 7. A methodof producing a reprint according to claim 1, wherein said arithmeticoperations upon said amount of exposure in said step (a) are performedon the basis of the following equation:

    log E.sub.i =log E.sub.Ni +C.sub.j (D.sub.Nj -D.sub.NNj)+γ.sub.j (D.sub.pj -D.sub.Npj)+KD·ID+Ki·Ii

where E: amount of exposure relative to said original-image film, E_(N): amount of exposure relative to a normal original-image film, C:correction factor based on the density of said original-image film,D_(N) : LATD of said original-image film, D_(NN) : LATD of saidoriginal-image film, γ: correction factor based on the density of saidoriginal-image film, D_(P) : density of said original-image film, D_(Np): density of said normal photographic paper, KD: number of steps ofselected density keys ( . . . -2, -1, 0, +1,+2, . . . ), Ki: number ofsteps of selected color keys ( . . . -2, -1, 0, +1, +2, . . . ), ID:amount of correction per step of said density key, Ii: amount ofcorrection per step of said color key, i: one of red, green and blue,and j: one of Y, M and C.
 8. A printing apparatus for producing areprint, comprising:a first data detecting means for detecting a set ofdata (a first set of data) relative to an image on an original-imagefilm; a second data detecting means for detecting a set of data (asecond set of data) relative to an image printed on a printed sheet ofphotographic paper from said original-image film; input means forinputting therethrough a set of correction data (a third set of data)relative to desired corrections to be made with respect to the colorcharacteristics of said image on said printed sheet; arithmetic meansfor, on the basis of said first, second and third sets of data,performing arithmetic operations upon the amount of exposure requiredfor printing said image on photographic paper from an original-imagefilm; and exposure control means for performing exposure control on thebasis of the results of said arithmetic operations to finish the colorcharacteristics of said image to be reprinted on said photographic paperso that said color characteristics includes said desired correctionsapplied to the color characteristics of said image printed on saidprinted sheet.
 9. A printing apparatus for producing a reprint accordingto claim 8 further comprising a light source for illuminating saidoriginal-image film and said printed sheet of photographic paper inorder to obtain said first and second set of data.
 10. A printingapparatus for producing a reprint according to claim 9 furthercomprising a carrier having a through-hole equivalent in size to oneimage frame of said original-image film for carrying said original-imagefilm to enable said one image frame to be located at a positioncorresponding to said through-hole.
 11. A printing apparatus forproducing a reprint according to claim 10, wherein said carrier has aphotographic-paper holding portion in which said printed sheet islocated.
 12. A printing apparatus for producing a reprint according toclaim 11, wherein said photographic-paper holding portion has anphotographic-paper exposing aperture formed adjacent to saidthrough-hole for allowing a printed surface of said printed sheet to beexposed to said light source.
 13. A printing apparatus for producing areprint according to claim 9, wherein said exposure control means isarranged to perform said exposure control by causing each filter of alight control filter device to move into and out of an exposure opticalpath extending between said light source and said photographic paper andat the same time opening and closing said exposure optical path by meansof a shutter.
 14. A printing apparatus for producing a reprint accordingto claim 13 wherein said first data detecting means includes densitysensor means for detecting density data relative to said image on saidoriginal-image film on the basis of light transmitted through saidoriginal-image film.
 15. A printing apparatus for producing a reprintaccording to claim 14, wherein said second data detecting means includesdensity sensor means for detecting density data relative to said imageformed on said printed sheet of photographic paper on the basis of lightreflected from said printed sheet.
 16. A printing apparatus forproducing a reprint according to claim 15 further comprising a mirrorfor reflecting light emitted from said light source to cause it toilluminate said printed sheet of photographic paper.
 17. A printingapparatus for producing a reprint, comprising:a carrier for carrying anoriginal-image film; a light source for projecting an image from saidoriginal-image film carried by said carrier onto photographic paper;film-image density detecting means for detecting the density (a firstdensity) of an image on said original-image film; paper-image densitydetecting means for detecting the density (a second density) of an imageprinted on said printed sheet from said original-image film; inputtingmeans arranged to input therethrough a correction density (a thirdcorrection density) required for making desired corrections with respectto the density of said image on said printed sheet; arithmetic meansfor, on the basis of said first, second and third densities, performingarithmetic operations upon the amount of exposure required for printingsaid image on said photographic paper from said original-image film; andexposure control means for performing exposure control on the basis ofthe results of said arithmetic operations to finish the density of saidimage to be reprinted on said photographic paper so that said densityincludes said desired corrections applied to said density of said imageprinted on said printed sheet.
 18. A printing apparatus for producing areprint according to claim 17, wherein said carrier has aphotographic-paper holding portion in which said printed sheet ofphotographic paper is located.
 19. A printing apparatus for producing areprint according to claim 18, wherein said carrier has a through-holeequivalent in size to one image frame of said original-image film and aphotographic-paper exposing aperture formed adjacent to saidthrough-hole for allowing a printed surface of said printed sheet to beexposed to said light source.
 20. A printing apparatus for producing areprint according to claim 19, wherein said photographic-paper exposingaperture is provided with a gray bottom surface.